At the time ... we were told Brown could be in rehab for up to 3 months -- sources told us "The rehab facility has been told to take him [Brown] apart and put him back together."

Now ... a little more than two weeks after entering the program ... Brown has checked out.

Brown's lawyer, Mark Geragos, tells TMZ his client needed to get out of the facility to start the community service he's required to perform in the Rihanna case. As you may recall, the judge would not accept the hoursChris claimed he had done, and made him do it all over again.

Geragos would not say if rehab did the trick, but did tell us Chris will continue in outpatient therapy.